Pyro-acoustic generator for protecting submarines and surface ships

ABSTRACT

The present invention provide a pyroacoustic device for protecting submarines or surface vessels, the device being characterized by the fact that it comprises: 
     a structure ( 240 ) suitable for forming a positioning device for controlled positioning under water; and 
     a case ( 100 ) connected to the positioning device, which case ( 100 ) contains: 
     a plurality of charges ( 110 ) each suitable for generating an acoustic effect; and 
     control means ( 125, 126; 140; 121 ) suitable for initiating said plurality of charges ( 110 ) in a controlled sequence.

The present invention relates to a pyroacoustic device constituting ajammer or decoy for protecting sub-marines or surface vessels.

Document U.S. Pat. No. 3,799,094 describes a pyrotechnic device fordiverting an underwater system. The device comprises a vehicle whichcarries a plurality of charges that are distributed generally over acylinder centered on a horizontal axis. The charges are urged radiallyoutwards by respective springs and they are freed cyclically by a roddriven in rotation by a shaft. Each of the charges has a membrane sothat as the charge sinks, the pressure on the payload increases, leadingat a given depth, to heating capable of causing initiation. The documentthus describes a device in accordance with the preamble of accompanyingclaim 1.

An object of the present invention is to propose a novel device that ismore effective than previously known devices against the homing systemsof torpedoes.

In the context of the present invention, this object is achieved by adevice comprising:

a structure suitable for forming a positioning device for controlledpositioning under water; and

a case connected to the positioning device, which case contains:

a plurality of charges each suitable for generating an acoustic effect;and

control means suitable for initiating said plurality of charges in acontrolled sequence characterized by the fact that the control means areadapted to define a time interval between initiation of two successivecharges lying in the range 0.2 seconds (s) to 0.5 s.

Other characteristics, objects, and advantages of the present inventionappear on reading the following detailed description and on examiningthe accompanying drawings, given as non-limiting examples, and in which:

FIG. 1 is a diagram of a case of the present invention, the top halfview being in longitudinal section and the bottom half view being a sideview;

FIG. 2 is a cross-section view of said structure;

FIG. 3 is a diagram of a unit charge of the invention;

FIG. 4 shows a variant, staggered arrangement of charges in accordancewith the invention;

FIG. 5 is a view similar to FIG. 1 showing a case constituting a secondembodiment of the invention;

FIG. 6 is a cross-section view through said case;

FIG. 7 is a view similar to FIG. 1 showing a case constituting a thirdembodiment of the invention;

FIG. 8 is a plan view of a tray of charges in the third embodiment;

FIG. 9 shows how charges are implemented in such a tray;

FIG. 10 shows a rocket designed to implement the device of theinvention;

FIG. 11 is a diagram showing the operation of the device of theinvention;

FIG. 12 is a cross-section view of a base for linking a buoy and thecase;

FIGS. 13 and 14 are longitudinal section views of the base respectivelyon section planes referenced XIII and XIV in FIG. 12;

FIG. 15 is a longitudinal section view of a rocket constituting anotherembodiment of the present invention;

FIG. 16 is a cross-section view of said rocket; and

FIG. 17 is a diagram showing the implementation sequence of thepyrotechnic device constituting this embodiment of the presentinvention.

In FIG. 1, there can be seen a circularly cylindrical case 100 having anaxis o—o that is vertical in use. The case 100 is connected to apositioning structure for controlled positioning under water. Such anunderwater positioning structure can be implemented in numerousdifferent ways. It preferably comprises an inflatable buoy 240 to whichthe case 100 is connected by a rope 2100, as described below.

However, in a variant, the positioning structure need not comprise aninflatable buoy, but may be a buoy that is already inflated or indeedany equivalent means suitable for floating on the water so as to supportthe case 100 by means of a rope 2100, or indeed any means suitable forcontrolling the sinking speed of the case 100. Thus, in a variant, thepositioning structure need not comprise an element that floats on thesurface of the water, but an element such as a parachute canopy adaptedfor controlling the rate at which the case 100 sinks in water.

The case 100 houses a plurality of charges 110 each adapted to generatean acoustic effect. As shown in FIG. 1, these charges 110 open out tothe outside surface of the case 100 and are distributed on a helixcentered on the axis o—o.

In addition, the case 100 houses means adapted to initiate the charges110 in succession at a controlled rate.

In FIGS. 1 and 2, these means are constituted by a motor and gear-boxunit 120 placed in the top portion of the case 100 and associated with abattery power supply 130. The motor unit 120 rotates a shaft 122centered on the axis o—o. The shaft 122 is not circularly cylindrical.It is engaged in a plate 124 which itself is engaged in a spiral guideformed inside the case 100 and it also carries at least one electricallyconductive brush 125, and preferably two electrically conductive brushes125 and 126, so that when the shaft 122 is rotated by the motor 120, thebrushes 125 and 126 come successively into contact with ignitor studs ofthe various charges 110.

Each of the charges 110 is preferably constituted by a generallycircularly cylindrical case 111 engaged radially towards the inside ofthe case 100. Each case 111 houses a sound composition 112. At itsradially inner end, each case 111 is provided with an ejector unit 113,inside which each case 111 further has a pyrotechnic delay 114. Inaddition, an electrical ignitor 115 is carried by the structure of thecase 100 receiving the charges 110 in register with each ejector unit113. Each ignitor 115 communicates with one ejector 113. Furthermore,each ignitor 115 has a power supply terminal in contact with theelectrically conductive case 100 and a second terminal that isaccessible to the path followed by the brushes 125 and 126.

Thus, the person skilled in the art will readily understand that when aninitiation voltage is applied between ground as constituted by the case100 and the brushes 125 and 126 by means of the shaft 122, then rotatingthe motor 120 serves to feed electricity to the ignitors 115 insuccession and consequently to eject the various charges 110successively by initiating their ejector units 113. The correspondingdelay 114 initiated by the ejector unit 113 serves at the end ofcombustion to initiate the associated sound composition 112.

By way of non-limiting example, the case 100 may contain 700 charges 110that are implemented at 0.25 s intervals.

FIG. 4 shows a variant arrangement in which the charges 110 are storedin a staggered configuration, thereby making it possible to reduce theheight of the case 100.

Preferably, sealing is provided between each charge 110 and the case100, e.g. by an o-ring 116 engaged on the radially inner end of eachcase 111.

Each case 111 is preferably held in the case 100 by means that aresuitable for releasing when the ejector unit 113 is implemented. Suchtemporary retention means can be implemented, for example, by means ofrespective toothed washers 117 engaged on respective studs 118 formed onthe radially outer surface of each case 111 and also engaging the insidesurface of each housing in the case 100 for receiving a charge 110.

FIG. 5 shows a variant embodiment in which the charges 110 are notdisposed in a helix, but as a plurality of disks that are stackedaxially. In addition, the electrical ignitors 115 described withreference to FIGS. 1 to 3 are replaced by percussion caps 130implemented by a rotary striker assembly 140 driven by the shaft 122 andcontrolled with timing supplied by an appropriate electronic circuit.

The general operation of the device shown in FIGS. 5 and 6 isessentially identical to that described with reference to FIGS. 1 to 4.

When the battery 130 is activated, it powers the motor 120. This rotatesthe rotary striker assembly 140 which is designed to strike thepercussion caps 130 automatically as it moves, and at an appropriaterate. On being struck, the caps 130 initiate the pyrotechnic ejectorunits 113 which fire the pyrotechnic delays 114 and eject the unitpyroacoustic charges 110.

At the end of its combustion, each pyrotechnic delay 114 initiates theassociated sound composition 112, thus creating the looked-for acousticeffect.

FIGS. 7 to 9 show another variant in which the case 100 receives aplurality of circular trays 150 that are stacked axially. As shown inFIGS. 8 and 9, each tray 150 itself receives a plurality of unit charges110, in chambers that open out axially into one of the main surfaces ofthe tray 150, extending orthogonally to the axis o—o in storage. Thecase 100 can thus house, for example, 30 trays each containing, forexample 18 charges 110.

The motor 120 is replaced by an electronic unit 121 connected via abundle of cables 128 to ejector units 1150 interposed between the trays150. In addition, each tray 150 carries an electrical ignitor 152,preferably in the central position.

Each charge 110 of the embodiment shown in FIGS. 7 to 9 has a body 111,preferably of plastics material, containing the sound composition 112,and a pyrotechnic delay 114.

The operating sequence of the device shown in FIGS. 7 to 9 is asfollows.

Activation of the battery 130 powers the electronics unit 121. Thisinitiates the electrical ignitors 152 of each tray with appropriatesequencing.

When an ignitor 152 is initiated, it ignites an associated ejector unit1150, thereby separating the tray 150, releasing its unit pyroacousticcharges and igniting the set of pyrotechnic delays 114 of the charges110. In any one tray, each delay 114 is of a different duration. At theend of its combustion, each pyrotechnic delay 114 initiates theassociated sound composition 112, thus creating the looked-for acousticeffect. The sequencing of the electronic unit 121 is such that the endof combustion of the last delay 114 in a given tray 150 corresponds tothe next tray 150 being initiated.

FIG. 10 shows a round of ammunition 200 suitable for being launched froma ship, for the purpose of implementing a countermeasure device of thepresent invention.

This round 200 comprises a body that is essentially circularlysymmetrical about an axis o—o. The body has a primary portion 210 and asecondary portion 250.

The primary portion 210 is situated at the tail end of the rocket 200.It preferably houses stabilizer fins 220, an engine 212 (which enginemay be a solid propellant motor), and preferably also a parachuteassembly 230.

The secondary portion 250 houses the payload of the charge whichcomprises the buoy structure 240 and the case 100 containing the soundcharges 110.

The round 200 preferably also has a pyrotechnic thruster 235 placedbetween the primary portion 210 and the secondary portion 250 toseparate the engine 212 from the payload 240/100 on initiation thereof.A second thruster situated in the nosecone of the rocket can also beused, after firing, to drive a piston for expelling the payload 240/100from its container tube so as to release the countermeasure device. Thefirst and second thrusters can be fired, for example, by means of anelectronic device.

Naturally, the representation given in accompanying FIG. 10 is givenpurely by way of non-limiting example. It can be varied in numerousways. Thus, for example, the parachute assembly 230 could be housed inthe secondary portion 250 instead of in the primary portion 210.

The engine 212 could indeed be associated with an asymmetrical parachutefor changing the trajectory of the engine 212 after the first thrusterhas been initiated so as to ensure that the engine does not interferewith the trajectory of the payload 240/100. Such an asymmetricalparachute may be as described in document FR-A-2 724 222.

The system of the present invention operates essentially as follows.

The round is fired with elevation and flight time determined accuratelyso that it reaches the desired range (FIGS. 11a and 11 b).

At an instant in flight as programmed by the launcher, the pyrotechnicsystem is initiated and the rear thruster is fired. This separates theengine 212 from the payload 240/100. The engine 212 is ejectedrearwards. The as-yet-undeployed brake parachute 230 and the payload240/100 are ejected forwards. A halyard interconnecting the above twoassemblies is paid out until it comes under tension.

The above-mentioned asymmetrical canopy fixed to said halyard deploysand inflates so as to change the trajectory of the engine 212 whichcontinues its trajectory under the asymmetrical canopy 124 until it hitsthe water.

When the above-mentioned halyard is tensioned, it pulls on a bagcontaining the canopy of the brake parachute 230, thereby paying out itssuspension lines. Once the suspension lines are tensioned, the bagreleases the asymmetrical canopy and there is no longer any connectionbetween the engine 212 and the payload 240/100. The canopy of the brakeparachute 230 inflates over very quickly and begins to brake the payload240/100 (FIG. 1c).

At the end of its trajectory, the payload 240/100 also reaches thesurface of the water.

When this happens, a sensor ensures that the buoy structure 240 isseparated from the case 100 and allows a link rope 2100 to be paid outbetween them.

The case 100 is initiated when the rope 2100 on which the case 100 issuspended from the buoy structure 240 becomes taut.

The case 100 and the unit charges 110 it contains operate as describedabove.

The buoy structure 240 may be inflated by any appropriate means onimpact with the water, for example by means of a CO2 capsule activatedby a striker which is itself released when a block of salt (e.g. NaCl)dissolves on coming into contact with the water.

The means providing temporary connection, prior to hitting the water,between the buoy structure 240 and the case 100 can be implemented innumerous ways.

FIGS. 12 to 14 show an embodiment of such means.

In these figures, there can be seen a base 260 designed to be fixed tothe top of the case 100.

The base 260 has a housing 262 receiving a coil of rope 2100.

At this level, one of the ends of the rope 2100 is connected to the base260 and consequently indirectly to the case 100. The other end of therope 2100 is connected to a stud 270 which is itself secured to the buoystructure 240.

The stud 270 is held to the top of the base 260 by temporary retainingmeans.

These temporary retaining means can be implemented in numerous ways.

By way of example, they may be shear pins adapted to break on impactagainst the water, so as to allow the buoy structure 240 to separatefrom the case 100 and the rope 2100 to be paid out.

However, in the preferred embodiment shown in the accompanying figures,the stud 270 is held firstly by an ejectable pin 280 and secondly bypegs 290 urged into engagement with the stud 270 by a rated force.

The pin 280 and the pegs 290 are placed in a top plate 264 of the base260.

The pin 280 is thus placed in a passage 265 formed radially in the plate264. At rest, the pin passes through a complementary bore formed in thestud 270 so as to prevent it from being withdrawn.

For the purpose of releasing the stud 270, the pin 280 is ejected onimpact against the water by gas pressure which is generated by anelectrical cap 282. For that purpose, and as can be seen in theaccompanying figures, the cap 282 is placed in a housing in the plate264 which is in communication with the passage 265 upstream from a notch281 formed in the pin 280.

Once the pin 280 has been withdrawn, the stud is held to the base 260only by the pegs 290.

It is preferable to provide two diametrically opposite pegs 290 placedin complementary passages 266 formed in the plate 264 at 90° to thepassage 265. The rounded radially inner heads of the pegs 290 rest in agroove formed in the periphery of the stud 270.

The pegs 290 are kept in engagement with the stud 270 under a ratedforce controlled by any appropriate means. By way of non-limitingexample, the pegs 290 can be held in the passages 266 by an arrangementof spring washers 292.

In a variant, the pin 280 can be withdrawn in flight, such that the pegs290 release the stud on impact against the water.

Naturally, the present invention is not limited to the particularembodiments described above, but extends to any variant within thespirit of the invention.

Thus, for example, although the unit charges 110 are implemented outsidethe case 100 in the embodiments described above, it is possible in avariant to envisage implementing them while they are in their storagepositions in the case, providing the cases 100 and 111 are adapted toavoid any risk of a charge 110 initiating an adjacent charge.

In the context of the present invention, the charges 110 are preferablyimplemented from the bottom of the case 100 upwards, so as to avoidcharges initiating one another, since the charges 110 have a tendency tosink after being released from the case 100.

In the context of the present invention, the time interval between twosuccessive charges 110 being initiated typically lies in the range 0.2 sto 0.5 s, and preferably in the range 0.2 s to 0.25 s.

In yet another variant, the case 100 can be covered in a frangible skin,e.g. of plastics material, adapted to break when a charge 110 isimplemented.

The embodiment shown in FIGS. 15 to 17 is described below.

As in the embodiments described above, the embodiment shown in FIGS. 15to 17 is adapted to emit an interrupted signal at high level thatresults from the successive timed pressure fronts created by pyrotechnicreactions.

In this variant, the pyroacoustic generator has a plurality ofsubcharges or submunitions 160 inter-connected by halyards 170. Thehalyards 170 also provide a link with the rope 2100 suspended from thebuoy 240 or from any equivalent positioning means.

Each submunition 160 is formed by an axial stack of a plurality of unitcharges or cans 110.

The halyards 170 are preferably adapted, as can be seen in FIG. 17, sothat once deployed the various sub-charges 160 form an almost continuousrope of unit charges 110. That is to say the top end of a givensub-munition 160 coincides substantially with the bottom end of theadjacent submunition 160 above it.

By way of non-limiting example, 19 submunitions 160 can thus beprovided, each having 60 unit charges 110.

The generator also has first delay means 162 adapted to initiate thevarious subcharges 160 in succession, and second delay means adapted toinitiate the various unit charges 110 of a submunition 160, likewise insuccession.

The first delay means 162 are preferably constituted by electronic meansintegrated in the base of each sub-munition 160. The second delay meansare preferably formed by pyrotechnic delays integrated in each of theunit charges 110, respectively.

In this way, each unit charge 110 is preferably in the form of acylindrical can containing a pyrotechnic composition and a pyrotechnicdelay body.

The delay means are preferably adapted to start initiating charges withthe bottom submunition 160, and within each submunition 160, to startinitiating charges with the bottom unit charge 110.

The delay means preferably define identical timing for the varioussubmunitions 160.

In addition, the delay means are preferably adapted so that the timebetween initiation of the last unit charge 110 in a given submunition160 and initiation of the first unit charge 110 in the followingsubmunition 160 is identical to the time interval between initiation ofunit charges within each of the submunitions 160.

The rocket 200 shown in FIG. 15 for implementing this device essentiallycomprises a rear portion 210 which includes an engine 212 associatedwith fins 220, and a front portion 250 which comprises, from its rearend towards its front end: a parachute compartment 230, a buoycompartment 240, and the payload constituted by sub-munitions 160 in acase or cylinder 100.

A pyrotechnic thruster 235 is placed between the rear portion 210 andthe front portion 250 to separate them when it is initiated. In thiscase also, it is preferable for a second thruster 2350 to be situated inthe nosecone 252 of the rocket to expel the submunitions 160 from thecylinder 100 on command.

In addition, the rocket preferably also has an asymmetrical parachute2300, as described above, for the purpose of changing the trajectory ofthe engine 212 after separation so as to ensure that the engine 212 doesnot interfere with the trajectory of the payload 160.

The submunitions 160, each of which comprises a stack of subcharges 110,are juxtaposed side by side in the cylinder 100, as can be seen in FIGS.15 and 16, in particular.

The device shown in FIGS. 15 to 17 essentially operates as follows.

In flight, a safety device and a power source are activated. After beingpositioned at the desired immersion depth, the nosecone 252 and the case100 are ejected, releasing the submunitions 160, as can be seen in FIGS.17a (before ejection of the cylinder 100) and 17 b (after ejection ofthe cylinder 100).

Thereafter, the operating sequence is controlled by long electronicdelays 162 associated respectively with the submunitions 160 operatingin parallel, and by short pyrotechnic delays integrated respectively ineach unit charge 110, the two delays operating in series. Each unitcharge 110 is initiated by a delay and operates to generate a pressurewave. The way these pressure waves are sequenced constitutes interruptednoise of long duration, suitable for jamming the sensors of torpedoes orof submarines.

The pyroacoustic device of the present invention can be adapted to jamsubmarines only or to jam both sub-marines and torpedoes. In the firstcase, the repetition rate is preferably less than half that of thesecond case, thereby enabling the device to operate for twice as long.

Furthermore, in the context of the present invention, it is possibleeither to provide for projecting the pyroacoustic device over aconsiderable distance, as described above, or else to release it orproject it over a short distance. In the first case, the pyroacousticgenerator is packaged so as to be carried by a rocket as describedabove. In the second case, constraints on mass and volume are different,so for substantially constant cost it is possible to double theoperating time of the pyroacoustic generator. In the second case, thedevice may be released by means of a pneumatic launcher or can simply bedropped by gravity overboard, manually or by means of adownwardly-sloping launcher. When put into place in the immediatevicinity of a vessel, the pyrotechnic sequence can either be initiatedimmediately, or it can be initiated after a delay. Under suchcircumstances, it must be possible, prior to release, to be able toprogram an initiation delay that may be as much as 5 minutes, andtypically, when four pyroacoustic generators are released in succession,their initiation delays should be 5 s, 80 s, 120 s, and 180 s.

What is claimed is:
 1. A pyroacoustic device for protecting submarinesor surface vessels, the device being characterized by the fact that itcomprises: a structure (240) suitable for forming a positioning devicefor controlled positioning under water; and a case (100) connected tothe positioning device, which case (100) contains: a plurality ofcharges (110) each suitable for generating an acoustic effect; andcontrol means (125, 126; 140; 121) suitable for initiating saidplurality of charges (110) in a controlled sequence characterized by thefact that the control means are adapted to define a time intervalbetween initiation of two successive charges lying in the range 0.2 s to0.5 s.
 2. A device according to claim 1, characterized by the fact thatthe time interval between initiation of two successive charges (110)lies in the range 0.2 s to 0.25 s.
 3. A device according to claim 1 or2, characterized by the fact that the case (100) is covered in a skinsuitable for being broken on each occasion a charge (110) isimplemented.
 4. A device according to claim 1, characterized by the factthat the control means comprise an assembly of electrically conductivebrushes (125, 126) displaced in register with ignitor studs (115) of thecharges (110).
 5. A device according to claim 1, characterized by thefact that the control means comprise percussion caps (130) implementedby a striker assembly (140) controlled with timing determined by anelectronic circuit.
 6. A device according to claim 1, characterized bythe fact that the control means comprise an electronic unit (121)controlling the timing of the charges (110).
 7. A device according toclaim 1, characterized by the fact that the charges (110) open out inthe outside surface of the case (100).
 8. A device according to claim 1,characterized by the fact that the charges (110) are distributed on ahelix centered on the axis O—O of the case (100).
 9. A device accordingto claim 1, characterized by the fact that the charges (110) arearranged in a staggered configuration.
 10. A device according to claim1, characterized by the fact that the charges (110) are disposed as aplurality of disks that are stacked axially.
 11. A device according toclaim 1, characterized by the fact that the case (100) houses aplurality of stacked circular trays (150) each housing the plurality ofcharges (110) in chambers which open out axially in one of the mainfaces of the trays (150).
 12. A device according to claim 11,characterized by the fact that the case (100) includes ejector units(1150) interposed between the trays (150).
 13. A device according toclaim 11, characterized by the fact that each tray (150) includes anelectrical ignitor (152) adapted to implement the charges (110).
 14. Adevice according to claim 1, characterized by the fact that each of thecharges (110) comprises a body (111) containing a sound composition(112) and a pyrotechnic delay (114).
 15. A device according to claim 11,characterized by the fact that each charge of each tray (150) comprisesa delay (114) and each delay has different duration than the other ones.16. A device according to claim 15, characterized by the fact that theelectronics unit (121) defines timing such that the end of combustion ofthe last delay (114) of a tray (150) corresponds to initiation of thefollowing tray (150).
 17. A device according to claim 1, characterizedby the fact that each charge (110) is associated with an ejector unit(113).
 18. A device according to claim 1, characterized by the fact thateach charge (110) is held in the case (100) by means adapted to give wayby use of an ejector unit (113).
 19. A device according to claim 1,characterized by the fact that said device comprises a plurality ofsubcharges or submunitions (160) interconnected by halyards (170) whichlink them to the structure (240), each submunition (160) being formed byan axial stack of said plurality of charges (110).
 20. A deviceaccording to claim 19, characterized by the fact that the halyards (170)are adapted so that the various subcharges (160) form a substantiallycontinuous cord of unit charges (110), i.e. the top end of a givensubmunition (160) coincides substantially with the bottom end of theadjacent submunition (160) above it.
 21. A device according to claim 19,characterized by the fact that said device further includes first delaymeans (162) adapted to initiate the submunitions (160) in succession,and second delay means adapted to initiate the charges (110) of asubmunition (160) in succession.
 22. A device according to claim 21,characterized by the fact that the first delay means (162) are formed byelectronic means integrated in each submunition (160), while the seconddelay means are formed by pyrotechnic delays respectively integrated ineach unit charge (110).
 23. A device according to claim 21,characterized by the fact that the delay means are adapted to commenceinitiation of the charges from the submunition (160) below, and within agiven submunition (160) from the charges (110) below.
 24. A deviceaccording to claim 21, characterized by the fact that the delay meansdefine timing that is identical for the various submunitions (160) andare adapted so that the time interval between initiation of a last oneof the plurality of charges (110) of a given submunition (160) andinitiation of a first one of a plurality of charges (110) of thefollowing submunition (160) is identical to the time intervals betweeninitiation of unit charges within each submunition (160).
 25. A deviceaccording to claim 1, characterized by the fact that the case (100) isplaced in a front portion (250) of a projectile whose rear portion (210)is fitted with an engine (212) and an asymmetrical canopy adapted todeflect the engine (212) onto a trajectory that is different from thatof the front portion after the front and rear portions have separated.26. A device according to claim 1, characterized by the fact that saiddevice includes a base (260) connected to the case (100) and possessinga housing (262) receiving a coil of rope (2100), one of the ends of therope (2100) being connected to the base (260) and consequentlyindirectly to the case (100), while the other end of the rope (2100) isconnected to a stud (270) itself secured to the structure (240) and heldto the top of the base (260) by temporary retaining means.
 27. A deviceaccording to claim 26, characterized by the fact that the temporaryretaining means comprise shear pins.
 28. A device according to claim 26,characterized by the fact that the temporary retaining means comprise anejectable pin (280) and pegs (290) urged to engage with the stud (270)by a rated force.
 29. A device according to claim 28, characterized bythe fact that it includes an electrical cap (282) suitable forcontrolling ejection of the pin (280).
 30. A device according to claim28, characterized by the fact that the pegs (290) are held in engagementwith the stud (270) by an arrangement of spring washers (292).
 31. Adevice according to claim 1, characterized by the fact that thestructure (240) comprises an inflatable buoy.
 32. A device according toclaim 1, characterized by the fact that the structure (240) comprises apositioning device adapted to control the sink rate of the payload. 33.A device according to claim 1, characterized by the fact that the devicecomprises means for defining delayed initiation of the sequence,starting from release of the device.
 34. A device according to claim 33,characterized by the fact that the means defining delayed initiation areprogrammable.
 35. A device according to claim 33, characterized by thefact that the means defining delayed initiation are adapted to controlinitiation of four pyroacoustic generators released in succession sothat their initiation delays are respectively 5 s, 80 s, 120 s, and 180s.
 36. A device according to claim 32 wherein said positioning devicecomprises a parachute canopy.